#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <sys/epoll.h>
#include <pthread.h>

constexpr int MAX_EVENT_NUM = 1024;
constexpr int BUFFER_SIZE = 10;

struct fds {
    int epollfd;
    int sockfd;
};

int setnonblocking(int fd) {
    int old_option = fcntl(fd, F_GETFL);
    int new_option = old_option | O_NONBLOCK;
    fcntl(fd, F_SETFL, new_option);
    return old_option;
}

void addfd(int epollfd, int fd, bool oneshot) {
    epoll_event event;
    event.data.fd = fd;
    event.events = EPOLLIN | EPOLLET;
    if (oneshot) {
        event.events |= EPOLLONESHOT;
    }
    epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &event);
    setnonblocking(fd);
}

void reset_oneshot(int epollfd, int fd) {
    epoll_event event;
    event.data.fd = fd;
    event.events = EPOLLIN | EPOLLET | EPOLLONESHOT;
    epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &event);
}

void *worker(void *args) {
    int sockfd = ((fds*)args)->sockfd;
    int epollfd = ((fds*)args)->epollfd;
    printf("start new thread to receive dara on fd: %d\n", sockfd);
    char buffer[BUFFER_SIZE];
    memset(buffer, 0, BUFFER_SIZE);
    while (1) {
        int ret = recv(sockfd, buffer, BUFFER_SIZE - 1, 0);
        if (ret == 0) {
            close(sockfd);
            printf("foreiner closed the connection\n");
            break;
        } else if (ret < 0) {
            if (errno == EAGAIN) {
                reset_oneshot(epollfd, sockfd);
                printf("read later");
                break;
            }
        } else {
            printf("get content: %s\n", buffer);
            sleep(5);
        }
    }
    printf("end thread receiving data on fd: %d\n", sockfd);
}

int main(int argc, char **argv) {
    if (argc != 3) {
        printf("usage: %s ip_address port_number\n", basename(argv[0]));
        return 1;
    }
    const char* ip = argv[1];
    int port = atoi(argv[2]);
    int ret = 0;
    struct sockaddr_in address;
    address.sin_family = AF_INET;
    address.sin_port = htons(port);
    inet_pton(AF_INET, ip, &address.sin_addr);

    int listenfd = socket(PF_INET, SOCK_STREAM, 0);
    assert(listenfd >= 0);
    ret = bind(listenfd, (struct sockaddr*)&address, sizeof(address));
    assert(ret != -1);
    ret = listen(listenfd, 5);
    assert(ret != -1);

    epoll_event events[MAX_EVENT_NUM];
    int epollfd = epoll_create(5);
    assert(epollfd != -1);
    addfd(epollfd, listenfd, false);

    while (1) {
        int ret = epoll_wait(epollfd, events, MAX_EVENT_NUM, -1);
        if (ret < 0) {
            printf("epoll failed.\n");
            break;
        }
        for (int i = 0; i < ret; i++) {
            int sockfd = events[i].data.fd;
            if (sockfd == listenfd) {
                struct sockaddr_in client;
                socklen_t client_addrlen = sizeof(client);
                int connfd = accept(sockfd, (struct sockaddr*)&client, &client_addrlen);
                addfd(epollfd, connfd, true);
            } else if (events[i].events & EPOLLIN) {
                pthread_t thread;
                fds fds_for_new_worker;
                fds_for_new_worker.epollfd = epollfd;
                fds_for_new_worker.sockfd = sockfd;
                pthread_create(&thread, NULL, worker, (void*)&fds_for_new_worker);
            } else {
                printf("something's wrong\n");
            }
        }
    }
    close(listenfd);
    return 0;
}